Venus makes two passes across the sun, eight years apart, every 122 years. While the next one will be in 2012, the next transit visible to North Americans will occur in 2117. As the sun is 30 times bigger, the planet is barely visible through special dark glasses.

JIm Tiller/AP

A fisherman and a pelican join Venus, dot at right, in a silhouette against the sun Tuesday in Flagler Beach, Fla.